Level 230 Summon1 Necro2 here.
On the Sorcerer end of things:
Level 5 Summons are quite resilient even with 0 points invested in SP. I can count on my Temple Shooter to endure long boss fights and blast big packs of dungeon mobs.
Salamion generally lasts the 60ish seconds he’s around for at skill level 1. Unless you want the blind attribute (req lvl 3) to annoy people in duels, he’s worth no more than one point.
As for Necromancer:
The Shuggoth is inferior to the Temple Shooter, offensively speaking, but is almost as resilient, and costs no SP to maintain.
Our Skeletons are extremely frail and die to one or two aoes from strong bosses. They’re still worth using against most bosses. The damage they deal really adds up if they survive for more than fifteen seconds. They are extremely useful while questing, farming and clearing trash. Just don’t expect them to last long - the skill as a 1 minute cooldown because you are intended to replace them frequently.
@Velkezar
The information you see in that help menu is outdated. The numbers there are from a time when Necromancers basically had a summon skill analogous to Sorcerer. This was removed in favor of the Shuggoth.